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//------------------------------------------------------------------------------
// GB_AxB_saxpy3_fineGus_notM_phase2: C<!M>=A*B, fine Gustavson, phase2
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2025, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
{
//--------------------------------------------------------------------------
// phase2: fine Gustavson task, C(:,j)<!M(:,j)>=A*B(:,j)
//--------------------------------------------------------------------------
// Hf [i] is 0 if M(i,j) not present or M(i,j)=0.
// 0 -> 1 : has already been done in phase0 if M(i,j)=1
// 1 -> 1 : to ignore, if M(i,j)=1
// 0 -> 3 : to lock, if i seen for first time
// 2 -> 3 : to lock, if i seen already
// 3 -> 2 : to unlock; now i has been seen
for ( ; pB < pB_end ; pB++) // scan B(:,j)
{
GB_GET_B_kj_INDEX ; // get index k of B(k,j)
GB_GET_A_k ; // get A(:,k)
if (aknz == 0) continue ;
GB_GET_B_kj ; // bkj = B(k,j)
// scan A(:,k)
for (int64_t pA = pA_start ; pA < pA_end ; pA++)
{
GB_GET_A_ik_INDEX ; // get index i of A(i,k)
GB_MULT_A_ik_B_kj ; // t = A(i,k) * B(k,j)
int8_t f ;
#if GB_IS_ANY_MONOID && GB_Z_HAS_ATOMIC_WRITE
//--------------------------------------------------------------
// ANY monoid with atomic write
//--------------------------------------------------------------
// the double complex ANY monoid cannot use this method
// lock state (3) not needed
// 0: not seen: update with new value, f becomes 2
// 1: masked, do nothing, f stays 1
// 2: already updated, do nothing, f stays 2
// 3: state not used, f can be 2
GB_ATOMIC_READ
f = Hf [i] ;
if (!f)
{
GB_ATOMIC_WRITE
Hf [i] = 2 ;
GB_Z_ATOMIC_WRITE_HX (i, t) ; // Hx [i] = t
}
#else
//--------------------------------------------------------------
// all other monoids
//--------------------------------------------------------------
GB_ATOMIC_READ
f = Hf [i] ; // grab the entry
#if GB_Z_HAS_ATOMIC_UPDATE
{
// the monoid can be done with a single atomic update
if (f == 2) // if true, update C(i,j)
{
GB_Z_ATOMIC_UPDATE_HX (i, t) ; // Hx [i] += t
continue ; // C(i,j) has been updated
}
}
#endif
if (f == 1) continue ; // M(i,j)=1; ignore C(i,j)
do // lock the entry
{
// do this atomically:
// { f = Hf [i] ; Hf [i] = 3 ; }
GB_ATOMIC_CAPTURE_INT8 (f, Hf [i], 3) ;
} while (f == 3) ; // lock owner of gets f=0 or 2
if (f == 0)
{
// C(i,j) is a new entry
GB_Z_ATOMIC_WRITE_HX (i, t) ; // Hx [i] = t
}
else // f == 2
{
// C(i,j) already seen
GB_Z_ATOMIC_UPDATE_HX (i, t) ; // Hx [i] += t
}
GB_ATOMIC_WRITE
Hf [i] = 2 ; // unlock the entry
#endif
}
}
}
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